The present invention relates to back checking arrangements, and more particularly, to a hydraulic back checking arrangement for an automatic door closer.
There are currently available several types of door closing mechanisms which provide a means for regulating the opening movement of a door and to prevent an over extension of the door opening commonly referred to as back checking.
In U.S. Pat. No. 5,050,268 issued to the inventor of the present application, a back checking arrangement is provided in a door closer which includes a loosely held resilient cushion bar which is engaged by a metallic shield abutting sliding cam plates during a final few degrees of opening of a door to provide an increasing resistance against further opening of the door. The shield engages a solid, but resilient cushion bar approximately 4.degree. prior to a normal full open position of the door. Selective thickness of the cushion bar provide either a 90.degree. full open position of the door or a 105.degree. full open position of the door without additional adjustment.
U.S. Pat. No. 4,064,589 to Bejarano, et al discloses a door closer in which an adjustable valve 132 is provided to regulate the back checking of the door which provides an adjustable shock absorber for the door which provides an adjustable shock absorber for the door as it reaches the fully opened position. This patent also discloses the use of a cushioning pad 157 to cushion a rearward movement of the carrier plate against the rear wall of the cam housing upon abrupt opening of the door past a normal/full open position. However, no means of attachment for the cushioning pad are disclosed.
U.S. Pat. No. 3,675,220 to Jentsch discloses a hydraulic cushioning device screwed through the door closer housing at a rear wall of the door closer housing, wherein a door closer cam forces plate-like members against the hydraulic cushioning device to slow the final stages of opening of the door. Mechanical energy of the door is dissipated to slow the door opening by throttling hydraulic fluid passing from the hydraulic cushioning device into the door closer housing, during compression of the hydraulic cushioning device.
U.S. Pat. No. 3,701,180 to Jentsch, et al discloses a door closer wherein a stud assembly comprising a compressible material replaces the hydraulic cushioning device disclosed in U.S. Pat. No. 3,675,220. Similar to U.S. Pat. No. 3,675,220, the study assembly is screwed through the housing.
U.S. Pat. No. 3,246,362 to A. Jackson discloses a door closer which relies on a compression of springs 31 as a back checking restraint and also relies on engagement between a cam 51 and cam follower rollers 43, 44 and 45 to provide a stop at a full open position of the door.
A back checking device which comprises a loosely captured cushion bar which provides an increasing resistance to the opening of a door during the last few degrees of travel until reaching a normal full open position, is new to the art.